Plug-in connectors for hollow sections of spacer frames for insulating glazing are known from practice in various embodiments. These plug-in connectors are designed, as a rule, for mechanically stable hollow sections made of metal. These are, e.g., extruded sections made of light metal or rolled sections or sections manufactured in another manner from steel plate. These plug-in connectors are less suited for more labile hollow sections made of plastic or from a combination of plastic and metal. Such pure plastic sections or combined sections are used for heat insulation purposes and are called warm-edge hollow sections.